The present invention relates to a device for affecting or modifying traveling speed of a motor vehicle having a traveling speed regulating means which compares an actual speed signal with a desired speed signal.
From German publication DE-OS No. 2,546,529 a traveling regulating device for a motor vehicle is known. In this prior art device, however, a new desired value for traveling speed suddenly is advanced when acceleration occurs. Since the traveling speed reacts relatively slowly there is the risk of regulating oscillations which may last at least several cycles after reaching the new desired value. In order to reduce such an overswing, the German publication DE-OS No. 2,537,415 teaches a regulator having a PD behavior. Due to different loads and due to variations in play in the linkage of setting member, the regulated speed after setting by such PD or P regulators is inaccurate. If in this case an I regulator is employed then the traveling comfort is impaired.
The German publication DE-OS No. 2,701,567 describes a traveling speed control device for motor vehicles in which the desired acceleration and deceleration can be selectively controlled by an acceleration pedal sensor. This control is achieved by evaluating according to a predetermined function the position of the acceleration pedal determined by the sensor and by using an integrator in the transmission path of the regulator for the traveling speed. The control of specified accelerations in this case is accomplished by regulating the actual speed to a desired or nominal value. This known device however requires an unconventional use of the acceleration pedal sensor and moreover there may result inaccuracies in setting the final speed after acceleration due to the increased reaction of the motor vehicle.
In the German publication DE-OS No. 2,842,023 a traveling speed regulator device for motor vehicles is described in which during acceleration the nominal or desired speed is adjusted to a ramp shaped curve of a nominal or desired speed so that a soft transition to each new end speed follows and accurate value of the end speed is always obtained. Nevertheless, this known device requires relatively expensive digital circuitry. In spite of its digital operation, however, it cannot be readily interfaced with an electronic fuel metering system, particularly it cannot use the existing computer in such a system.